I have an Android phone and my wife has an iPhone. Google Home uses my phone phone to automatically determine if I'm home or away and it seems to work pretty well. However, I'm having trouble with my wife's phone. I set her "Location Access Settings" for the Google Home app to "Always" and it seems to work fine for a few days. Then, it doesn't. When I check back, her "Location Access Settings" for the Google Home app seems to revert to "While Using the App" and I can't figure out why.
(Below is the screen I edit on my wife's iPhone.)
I've updated her phone's operating system and uninstalled Nest, thinking that maybe there was something weird with Next and Google Home both trying to manage presence settings. That didn't work, though. It just seems that after a few days her phone always switches to while using the app. I haven't tried uninstalling and reinstalling Google Home, though.